Eocene magmatism in the Himalaya: Response to lithospheric flexure during early Indian collision?

Eocene mafic magmatism in the Himalaya provides a crucial window for probing the evolution of crustal anatexis processes within the lower plate in a collisional orogen. We report geochemical data from the earliest postcollision ocean-island basalt-like mafic dikes intruding the Tethyan Himalaya near the northern edge of the colliding Indian plate. These dikes occurred coeval, and spatially overlap, with Eocene granitoids in the cores of gneiss domes and were likely derived from interaction between melts from the lithosphere-asthenosphere boundary and the Indian continental lithosphere. We propose that these mafic magmas were emplaced along lithospheric fractures in response to lithospheric flexure during initial subduction of the Indian continent and that the underplating of such mafic magmas resulted in orogen-parallel crustal anatexis within the Indian continent. This mechanism can explain the formation of coeval magmatism and the geologic evolution of a collisional orogen on both sides of the suture zone.

Automated summary

Eocene mafic magmatism in the Himalaya is important for understanding crustal anatexis processes within collisional orogens. Geochemical data from mafic dikes intruding the Tethyan Himalaya indicate interaction between lithospheric and asthenospheric melts. These magmas were emplaced along lithospheric fractures during initial subduction, resulting in orogen-parallel crustal anatexis.